1. Field of the Invention
The present invention relates generally to the detection of cancerous tissues, and, more particularly, to a method and apparatus for detecting cancerous tissues of the epithelium of a human sigmoid colon and rectum, and, as well, detecting early changes in such epithelium which indicate the epithelium will eventually evolve into polyps or cancer.
2. Description of Related Art
It has been suggested in the past to determine the presence of certain cancerous tissue in a human by passing an electric current of predetermined value through suspected tissue and determining the electrical impedance of such tissue as compared to normal tissue. Similarly, it has also been suggested in the past that premalignant tissues which would, if nothing intervened, result in either polyps or cancerous tissue could be detectable by determining a specific change in tissue electrical impedance relative to the impedance of normal tissues.
It is generally considered in the prior art that human tissues composed of abnormal cells (i.e., tumor, carcinoma) exhibit an increased electrical impedance as compared to the impedance of the same tissues, if healthy. Exemplary of approaches to detection of cancerous tissues following these considerations are U.S. Pat. No. 4,729,385, PROBE AND METHOD OF USE FOR DETECTING ABNORMAL TISSUES by R. J. Davies and R. D. Juncosa and U.S. Pat. No. 4,690,152, APPARATUS FOR EPITHELIAL TISSUE IMPEDANCE MEASUREMENTS by R. D. Juncosa. Also, Arch. Geschwulstforsch 58: 105-111 (1988) discusses electrical parameters of the cervical epithelium, and European Surgical Research (22):86-92 (1990) is concerned with the bio-impedance of breast tumors.
In none of the known prior work has there been provided a fully satisfactory technique for determining when a tissue is cancerous by measuring its transepithelial electrical impedance. Moreover, even less correlation has been established in the past as to when a tissue that, by other tests, is not presently in a malignant stage, could by testing be found to determine or red flag the fact that it would eventually evolve into cancerous tissue.